server/rune.c: If skill is NULL in dispel_rune(), just return as server
will otherwise crash in trap_disarm()
server/spell_util.c: Fix bug in that runes that hold other spells (glyphs,
firetraps, magic runes, etc) do not find a skill object, and thus
player doesn't get exp. Instead, for runes, try to find owner, and
then the relevant skill object.
MSW 2006-11-18